Hydrometallurgical processes to extract metal values from ore, such as pressure oxidation and pressure oxidative leaching, take place in specialized reactor vessels, such as an autoclave. Pressure oxidation in an autoclave typically requires the introduction and dispersion of oxygen gas through a sparger. Existing spargers typically include a J-shaped lance extending downwards into the vessel, through the vapour zone and into slurry in the vessel. The lower end of the lance is often curved in a J-shape so as to disperse oxygen below agitators located in the slurry. A flanged joint known as a fire break is located near the top of the vessel to prevent fire propagation through the vessel nozzle.
A difficulty with providing for oxygen sparging is that the environment within the vessel is highly corrosive. To avoid combustion of the sparger, the sparger is typically constructed of duplex and super-duplex stainless steel alloys or austentic stainless steel. Unfortunately, existing spargers have a short service life owing to the fact that the material used to create the sparger is subject to corrosion in the environment of the reactor vessel.
Corrosion resistant materials, such as reactive metals like titanium or niobium, are unsuitable for use creating an oxygen sparger since they are highly pyrophoric. Accordingly, use of these materials, while addressing the issue of corrosion, creates a risk of fire.
There does not appear to be a material that is both suitably corrosion resistant and non-combustible. Accordingly, there remains a need for a sparger capable of operating under elevated temperature and corrosive conditions.